A wireless LAN data transceiver that uses radio waves to connect a wired network with wireless stations.

ad hoc network

A wireless network composed of stations without access points.

AES-CCMP

Based on the Advanced Encryption Standard (AES) defined in the National Institute of Standards and Technology's
FIPS Publication 197, AES-CCMP is a symmetric block cipher that can encrypt and decrypt data using keys of 128, 192, and 256 bits. AES-CCMP is superior to WEP encryption and is defined in the IEEE 802.11i standard.

antenna gain

The gain of an antenna is a measure of the antenna's ability to direct or focus radio energy over a region of space. High gain antennas have a more focused radiation pattern in a specific direction.

ampdu

Aggregate MAC protocol unit. An A-MPDU is a structure containing multiple MPDUs transported as a single PSDU by the PHY.

associated

A station is configured properly to allow it to wirelessly communicate with an Access Point.

B

beacon

A wireless LAN packet that signals the availability and presence of the wireless device.

BID

Bridge identifier used in spanning tree calculations. The BID contains the bridge MAC address and its spanning tree priority value. If all bridges in the spanning tree are assigned the same priority, the bridge with the lowest MAC address becomes the spanning tree root.

BOOTP

Boot Protocol. A protocol used for the static assignment of IP addresses to devices on the network.

BPDU

Bridge protocol data unit. When spanning tree is enabled, bridges send and receive spanning-tree frames, called BPDUs, at regular intervals and use the frames to maintain a loop-free network.

BPSK

A modulation technique used by IEEE 802.11b-compliant wireless LANs for transmission at 1 Mbps.

broadcast packet

A single data message (packet) sent to all addresses on the same subnet.

C

CCK

Complementary code keying. A modulation technique used by IEEE 802.11b-compliant wireless LANs for transmission at 5.5 and 11 Mbps.

CCKM

Cisco Centralized Key Management. Using CCKM, authenticated client devices can roam from one access point to another without any perceptible delay during reassociation. An access point on your network acts as a subnet context manager (SCM) and creates a cache of security credentials for CCKM-enabled client devices on the subnet. The SCM's cache of credentials dramatically reduces the time required for reassociation when a CCKM-enabled client device roams to a new access point.

cell

The area of radio range or coverage in which thewireless devices can communicate with the base station. The size of the cell depends upon the speed of the transmission, the type of antenna used, and the physical environment, as well as other factors.

client

A radio device that uses the services of an Access Point to communicate wirelessly with other devices on a local area network.

The range of data transmission rates supported by a device. Data rates are measured in megabits per second (Mbps).

dBi

A ratio of decibels to an isotropic antenna that is commonly used to measure antenna gain. The greater the dBi value, the higher the gain, and the more acute the angle of coverage.

DFS

Dynamic Frequency Selection. In some regulatory domains, 5-GHz radios are required to use DFS to avoid interfering with radar signals.

DHCP

Dynamic host configuration protocol. A protocol available with many operating systems that automatically issues IP addresses within a specified range to devices on the network. The device retains the assigned address for a specific administrator-defined period.

dipole

A type of low-gain (2.2-dBi) antenna consisting of two (often internal) elements.

domain name

The text name that refers to a grouping of networks or network resources based on organization-type or geography; for example: name.com—commercial; name.edu—educational; name.gov—government; ISPname.net—network provider (such as an ISP); name.ar—Argentina; name.au—Australia; and so on.

DNS

Domain Name System server. A server that translates text names into IP addresses. The server maintains a database of host alphanumeric names and their corresponding IP addresses.

DSSS

Direct sequence spread spectrum. A type of spread spectrum radio transmission that spreads its signal continuously over a wide frequency band.

E

EAP

Extensible Authentication Protocol. An optional IEEE 802.1x security feature ideal for organizations with a large user base and access to an EAP-enabled Remote Authentication Dial-In User Service (RADIUS) server.

Ethernet

The most widely used wired local area network. Ethernet uses carrier sense multiple access (CSMA) to allow computers to share a network and operates at 10, 100, or 1000 Mbps, depending on the physical layer used.

F

file server

A repository for files so that a local area network can share files, mail, and programs.

firmware

Software that is programmed on a memory chip.

G

gateway

A device that connects two otherwise incompatible networks together.

GHz

Gigahertz. One billion cycles per second. A unit of measure for frequency.

I

IEEE

Institute of Electrical and Electronic Engineers. A professional society serving electrical engineers through its publications, conferences, and standards development activities. The body responsible for the Ethernet 802.3 and wireless LAN 802.11 specifications.

infrastructure

The wired Ethernet network.

IP address

The Internet Protocol (IP) address of a station.

IP Subnet Mask

The number used to identify the IP subnetwork, indicating whether the IP address can be recognized on the LAN or if it must be reached through a gateway.
This number is expressed in a form similar to an IP address; for example: 255.255.255.0.

isotropic

An antenna that radiates its signal in a spherical pattern.

M

MAC

Media Access Control address. A unique 48-bit number used in Ethernet data packets to identify an Ethernet device, such as an access point or your client adapter.

MBSSID

Multiple basic SSID. Each multiple basic SSID is assigned a unique MAC address. You use multiple BSSIDs to assign a unique DTIM setting for each SSID and to broadcast SSIDs in beacons (one SSID per beacon).

modulation

Any of several techniques for combining user information with a transmitter's carrier signal.

multipath

The echoes created as a radio signal bounces off of physical objects.

multicast packet

A single data message (packet) sent to multiple addresses.

O

omni-directional

This typically refers to a primarily circular antenna radiation pattern.

A basic message unit for communication across a network. A packet usually includes routing information, data, and sometimes error detection information.

Q

Quadruple Phase Shift Keying

A modulation technique used by IEEE 802.11b-compliant wireless LANs for transmission at 2 Mbps.

R

range

A linear measure of the distance that a transmitter can send a signal.

receiver sensitivity

A measurement of the weakest signal a receiver can receive and still correctly translate it into data.

RF

Radio frequency. A generic term for radio-based technology.

roaming

A feature of some Access Points that allows users to move through a facility while maintaining an unbroken connection to the LAN.

RP-TNC

A connector type unique to Cisco Aironet radios and antennas. Part 15.203 of the FCC rules covering spread spectrum devices limits the types of antennas that may be used with transmission equipment. In compliance with this rule, Cisco Aironet, like all other wireless LAN providers, equips its radios and antennas with a unique connector to prevent attachment of non-approved antennas to radios.

S

Spread Spectrum

A radio transmission technology that spreads the user information over a much wider bandwidth than otherwise required in order to gain benefits such as improved interference tolerance and unlicensed operation.

SSID

Service Set Identifier (also referred to as Radio Network Name). A unique identifier used to identify a radio network and which stations must use to be able to communicate with each other or to an access point. The SSID can be any alphanumeric entry up to a maximum of 32 characters.

T

transmit power

The power level of radio transmission.

U

UNII

Unlicensed National Information Infrastructure—regulations for UNII devices operating in the 5.15 to 5.35 GHz and 5.725 to 5.825 GHz frequency bands.

UNII-1

Regulations for UNII devices operating in the 5.15 to 5.25 GHz frequency band.

UNII-2

Regulations for UNII devices operating in the 5.25 to 5.35 GHz frequency band.

UNII-3

Regulations for UNII devices operating in the 5.725 to 5.825 GHz frequency band.

unicast packet

A single data message (packet) sent to a specific IP address.

W

WDS

Wireless Domain Services. An access point providing WDS on your wireless LAN maintains a cache of credentials for CCKM-capable client devices on your wireless LAN. When a CCKM-capable client roams from one access point to another, the WDS access point forwards the client's credentials to the new access point with the multicast key. Only two packets pass between the client and the new access point, greatly shortening the reassociation time.

WEP

Wired Equivalent Privacy. An optional security mechanism defined within the 802.11 standard designed to make the link integrity of wireless devices equal to that of a cable.